ORGANIC LETTERS
Efficient Heterogeneous Oxidation of Alkylarenes with Molecular Oxygen Keigo Kamata,† Jun Kasai,‡ Kazuya Yamaguchi,†, ‡ and Noritaka Mizuno*,†,
2004 Vol. 6, No. 20 3577-3580 ‡
Core Research for EVolutional Science and Technology, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan, and Department of Applied Chemistry, School of Engineering, The UniVersity of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
[email protected] Received July 27, 2004
ABSTRACT
Ru(OH)x/Al2O3 efficiently catalyzes the heterogeneous aerobic oxygenation or oxidative dehydrogenation of alkylarenes to give the corresponding oxygenated or dehydrogenated products. Catalyst/product separation is very easy, and the recovered catalyst is reusable with retention of the high catalytic performance.
The oxidation of alkylarenes has received much attention. For example, it has been reported that the polyacene derivatives can be applied to organic semiconductors and transistors1 and that dehydrogenation of the corresponding alkylarenes is one of the most reliable candidates for the synthesis of polyacene derivatives among various synthetic procedures.2 Since dehydrogenation of alkylarenes typically requires stoichiometric oxidation reagents and/or relatively forced reaction conditions,3 alternative efficient procedures, i.e., catalytic aerobic oxidation systems, have been desired.4 The development of the catalytic oxygenation of alkylarenes with molecular oxygen is also technologically and environmentally important. Although numerous catalytic systems †
Japan Science and Technology Agency. The University of Tokyo. (1) (a) Scho¨n, J. H.; Kloc, Ch.; Bucher, E.; Batlogg, B. Nature 2000, 403, 408. (b) Dimitrakopoulos, C. D.; Purushothaman, S.; Kymissis, J.; Callegari, A.; Shaw, J. M. Science 1999, 283, 822. (c) Afzali, A.; Dimitrakopoulos, C. D.; Breen, T. L. J. Am. Chem. Soc. 2002, 124, 8812. (2) Fu, P. P.; Harvey, R. G. Chem. ReV. 1978, 78, 317. (3) (a) Nagano, T.; Yokoohji, K.; Hirobe, M. Tetrahedron Lett. 1984, 25, 965. (b) Wang, K.; Mayer, J. M. J. Am. Chem. Soc. 1997, 119, 1470. (c) Lockwood, M. A.; Blubaugh, T. J.; Collier, A. M.; Lovell, S.; Mayer, J. M. Angew. Chem., Int. Ed. 1999, 38, 225. (d) Takahashi, T.; Kitamura, M.; Shen, B.; Nakajima, K. J. Am. Chem. Soc. 2000, 122, 12876. (4) (a) Tanaka, H.; Ikeno, T.; Yamada, T. Synlett 2003, 576. (b) Nakamichi, N.; Kawabata, H.; Hayashi, M. J. Org. Chem. 2003, 68, 8272. ‡
10.1021/ol0485363 CCC: $27.50 Published on Web 09/03/2004
© 2004 American Chemical Society
using nitrous oxide,5 sulfoxide,6 and molecular oxygen in combination with reducing agents7 or radical initiators8 have been reported, there are only a few examples of such liquidphase oxidation with molecular oxygen as the sole oxidant.9 In addition, the use of solid or supported catalysts is more desirable because of their easy isolation from the products and recycling.10 In these contexts, it is desirable to develop the heterogeneously catalyzed aerobic oxidation of alkylarenes with high turnover numbers under mild reaction conditions. We report in this paper the efficient heterogeneous aerobic oxygenation and oxidative dehydrogenation of alkylarenes catalyzed by Ru(OH)x/Al2O3. (5) (a) Ben-Daniel, R.; Neumann, R. Angew. Chem., Int. Ed. 2003, 42, 92. (b) Hashimoto, K.; Tanaka, H.; Ikeno, T.; Yamada, T. Chem. Lett. 2002, 582. (6) Khenkin, A. M.; Neumann, R. J. Am. Chem. Soc. 2002, 124, 4198. (7) Maikap, G. C.; Guhathakurta, D.; Iqbal, J. Synlett 1995, 189. (8) Ishii, Y.; Nakayama, K.; Takeno, M.; Sakaguchi, S.; Iwahama, T.; Nishiyama, Y. J. Org. Chem. 1995, 60, 3934. (9) (a) Khenkin, A. M.; Weiner, L.; Wang, Y.; Neumann, R. J. Am. Chem. Soc. 2001, 123, 8531. (b) Feldman, D.; Rabinovitz, M. J. Org. Chem. 1988, 53, 3779. (c) Matsushita, T.; Ebitani, K.; Kaneda, K. Chem. Commun. 1999, 265. (d) Holliday, R. L.; Jong, B. Y. M.; Kolis, J. W. J. Supercrit. Fluids 1998, 12, 255. (10) (a) Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice; Oxford University Press: London, 1998. (b) Sheldon, R. A. Green Chem. 2000, 2, G1. (c) Anastas, P. T.; Bartlett, L. B.; Kirchhoff, M. M.; Williamson, T. C. Catal. Today 2000, 55, 11.
Table 1. Oxidation of Xanthene and 9,10-Dihydroanthracene with Molecular Oxygen by Various Catalystsa xanthene entry
catalyst
conversion (%)
1 2 3 4 5 6 7 8 9 10 11d 12d 13e 14e 15f 16f 17f 18f 19f 20f
Ru(OH)x/Al2O3 Ru(OH)3‚nH2O RuO2 RuCl2(PPh3)3 RuCl2(DMSO)4 RuCl2(bpy)2 RuCl3‚nH2O [Ru3O(OAc)6(H2O)3](OAc) K2RuCl6 nPr4NRuO4 Al2O3 Al2O3 treated with NaOH Ru(OH)3‚nH2O + Al2O3 RuCl3‚nH2O + Al2O3 Pd(OH)x/Al2O3 Rh(OH)x/Al2O3 Pt(OH)x/Al2O3 V(OH)x/Al2O3 Fe(OH)x/Al2O3 Cu(OH)x/Al2O3
>99
